This application relates to a vascular surgical apparatus, and more particularly to a minimally invasive device for removing plaque or other deposits from the interior of a vessel.
The vascular disease of atherosclerosis is the buildup of plaque or substances inside the vessel wall which reduces the size of the passageway through the vessel, thereby restricting blood flow. Such constriction or narrowing of the passage in the vessel is referred to as stenosis. In the case of peripheral vascular disease, which is atherosclerosis of the vascular extremities, if the vessel constriction is left untreated, the resulting insufficient blood flow can cause claudication and possible require amputation of the patient""s limb. In the case of coronary artery disease, if left untreated, the blood flow through the coronary artery to the myocardium will become inadequate causing, myocardial infarction and possibly leading to stroke and even death.
There are currently several different treatments for treating arterial disease. The most invasive treatment is major surgery. With peripheral vascular diseases, such as occlusion of the tibial artery, the major surgery involves implantation and attachment of a bypass graft to the artery so the blood flow will bypass the occlusion. The surgery involves a large incision, e.g. a 10 inch incision in the leg, is expensive and time consuming for the surgeon, increases patient pain and discomfort, results in a long patient recovery time, and has the increased risk of infection with the synthetic graft.
Major surgery for treating coronary artery disease is even more complex. In this surgery, commonly referred to as open heart surgery, a bypass graft connects the heart to the vessel downstream of the occlusion, thereby bypassing the blockage. Bypass surgery requires opening the patient""s chest, is complex, has inherent risks to the patient, is expensive and requires lengthy patient recovery time. Bypass surgery also requires use of a heart lung machine to pump the blood as the heart is stopped, which has its own risks and disadvantages. Oftentimes, the saphenous vein in the patient""s leg must be utilized as a bypass graft, requiring the additional invasive leg incision which further complicates the procedure, increases surgery time, lengthens the patient""s recovery time, can be painful to the patient, and increases the risk of infection.
Attempts to minimize the invasiveness of coronary bypass surgery are currently being developed and utilized in certain instances. These typically include cracking a few ribs and creating a xe2x80x9cwindow approachxe2x80x9d to the heart. Although the window approach may reduce patient trauma and recovery time relative to open heart surgery, it still requires major surgery, and is a complicated and difficult surgery to perform due to limited access and limited instrumentation for successfully performing the operation. Attempts to avoid the use of a heart lung machine by using heart stabilization methods is becoming more accepted, but again, this does not avoid major surgery.
Due to these problems with major peripheral or coronary vascular surgery, minimally invasive procedures have been developed. Balloon angioplasty is one of the minimally invasive methods for treating vessel occlusion/obstructions. Basically, a catheter having a balloon is inserted through the access artery, e.g. the femoral artery in the patient""s leg or the radial artery in the arm, and advanced through the vascular system to the occluded site over a wire. The deflated balloon is placed at the occlusion and the balloon is inflated to crack and stretch the plaque and other deposits to expand the opening in the vessel. Balloon angioplasty, especially in coronary surgery, is frequently immediately followed by insertion of a stent, a small metallic expandable device which is placed inside the vessel wall to retain the opening which was created by the balloon. Balloon angioplasty has several drawbacks including difficulty in forcing the balloon through the partially occluded passageway if there is hard occlusion, the risk involved in cutting off blood flow when the balloon is fully inflated, and the frequency of restenosis after a short period of time since the plaque is essentially stretched or cracked and not removed from the vessel wall or because of the development of intimal hyperplasia.
Another minimally invasive technique used to treat arteriosclerosis is referred to as atherectomy and involves removal of the plaque by a cutting or abrading instrument. This technique provides a minimally invasive alternative to bypass surgery techniques described above as well as can provide an advantage over balloon angioplasty methods in certain instances. Atherectomy procedures typically involve inserting a cutting or ablating device through the access artery, e.g. the femoral artery or the radial artery, and advancing it through the vascular system to the occluded region, and rotating the device at high speed to cut through or ablate the plaque over the wire. The removed plaque or material can then be suctioned out of the vessel or be of such fine diameter that it is cleared by the reticuloendothelial system. Removal of the plaque in an atherectomy procedure has an advantage over balloon angioplasty plaque displacement since it debulks the material.
Examples of atherectomy devices in the prior art include U.S. Pat. Nos. 4,990,134, 5,681,336, 5,938,670, and 6,015,420. These devices have elliptical shaped tips which are rotated at high speeds to cut away the plaque and other deposits on the interior vessel wall. A well-known device is marketed by Boston Scientific Corp. and referred to as the Rotablator. As can be appreciated, in these devices, the region of plaque removal is dictated by the outer diameter of the cutting tip (burr) since only portions of the plaque contacted by the rotating tip are removed. Obviously, the greater the area of plaque removed, the larger passageway created through the vessel and the better the resulting blood flow.
Since these atherectomy tips need to be inserted through an introducer sheath or catheter to the target site, the larger the tip, the larger the diameter of the introducer sheath required. However, larger introducer sheaths increase the risk of trauma to the patient, are harder to navigate through the vessels, and create larger incisions (require larger puncture sites) into the access artery which cause additional bleeding and complicate closure of the incision at the end of the procedure. On the other hand, if the introducer sheath is too small, then the rotating tip will not be able to remove a sufficient area of obstructive deposits and the vessel will remain partially occluded. Thus, a tradeoff must be made between these two opposing goals: larger cutting tip but smaller introducer sheath.
This problem was recognized for example in U.S. Pat. Nos. 5,217,474 and 6,096,054 which attempted solutions involved expandable cutting tips. These tips however are quite complex and require additional expansion and contraction steps by the surgeon.
The need therefore exists to provide an improved atherectomy cutting tip to obtain an optimal balance between the competing objectives of the smallest introducer sheath size to facilitate insertion and reduce trauma to the vessel and the largest atherectomy tip size to remove a larger region of plaque or other deposits from the vessel wall.
The present invention provides a uniquely configured atherectomy tip which enables a smaller sized introducer sheath to be utilized without sacrificing the region of plaque being removed from the interior of the vessel.
More specifically, the present invention provides a surgical apparatus for removing deposits from an interior of a vessel comprising a rotatable shaft and a rotatable tip mounted to the shaft and rotatable about its longitudinal axis upon rotation of the shaft to remove deposits from the interior of the vessel. The tip has a distal portion, a proximal portion and an intermediate portion between the distal and proximal portions. The intermediate portion is defined by a plurality of transverse cross-sectional areas, wherein each transverse cross-sectional area defines first and second axes substantially perpendicular to each other to define a width dimension along the first axis and a height dimension along the second axis. The height dimension is greater than the width dimension.
Preferably, the height progressively increases towards the proximal portion and the width progressively decreases toward the proximal portion. An opening in a sidewall of the tip for removal of the cut plaque can be provided. The distal portion may have a bullet shaped nose. A plurality of longitudinally extending grooves or cutouts can be formed in an outer surface of the tip to form an ablation surface.
The present invention also provides a surgical apparatus for removing deposits such as plaque from an interior of a vessel, comprising a rotatable shaft having a lumen extending therethrough dimensioned to receive a guidewire and a tip mounted on the rotatable shaft for rotation about its longitudinal axis upon rotation of the shaft. The tip has a distal portion, a proximal portion and an intermediate portion between the distal and proximal portions. The tip includes a guidewire lumen for receiving a guidewire to enable over the wire insertion of the shaft and tip. The distal portion of the tip is substantially circular in cross-section and the intermediate and proximal portions are non-circular in cross-section.
Preferably, the non-circular cross-section of the intermediate and proximal portions is defined by first and second opposing walls separated by a first distance and third and fourth opposing walls separated by a second distance, wherein the first distance is greater than the second distance. The first distance preferably progressively increases towards the proximal portion and the second distance progressively decreases towards the proximal portion. The third and fourth walls preferably have a substantially linear portion and the first and second walls are preferably curved.
The present invention also provides a vascular surgical apparatus for removing deposits such as plaque from a vessel comprising a rotatable shaft with a distal section and a distal tip mounted on the distal section and rotatable upon rotation of the shaft to remove deposits in a circumferential area determined by a major diameter of the distal tip as it rotates on its axis. The distal tip has a proximal portion, a distal portion and an intermediate portion between the proximal and distal portions, wherein each transverse cross-section of the tip defines a circumference, a first diameter, and a second diameter substantially orthogonal to the first diameter. The first diameter of the intermediate portion is greater than the first diameter of the distal portion and the circumference at the distal portion is substantially equal to the circumference at the intermediate portion.
Preferably, the first diameter of the intermediate portion is greater than a second diameter of the intermediate portion and the first diameter of the distal portion is substantially equal to the second diameter of the distal portion. The intermediate portion has opposing scalloped portions to form the smaller second diameter region.
A method for removing deposits from an interior of a vessel is also provided comprising the steps of:
providing an introducer sheath having a first internal diameter;
providing a deposit removal tip having a rotating shaft and a rotating tip at the distal end of the shaft, the rotating tip having an outer diameter greater than the internal diameter of the sheath and further having first and second opposing narrowed regions;
inserting the introducer sheath through a skin incision and into a vessel, the sheath forming an incision opening at least equal to the external diameter of the sheath;
inserting the rotating tip into the introducer sheath to deform the introducer sheath to accommodate the larger outer diameter of the rotating tip;
moving the tip out through a distal opening in the introducer sheath, thereby allowing the introducer sheath to return to its undeformed configuration;
advancing the distal tip adjacent the deposits to be removed; and
rotating the tip at high speed to contact and remove the deposits from the interior of the vessel.